This invention relates to service tees for tapping plastic pipe. In one of its aspects this invention relates to cutters used in conjunction with tapping tees. In another of its aspects this invention relates to minimizing frictional contact between the external diameter of the cutting plug and the plastic pipe being tapped.
Plastic piping has come into wide usage as a replacement for metal piping. In most instances the combination of strength and flexibility of the plastic pipe makes this material equal to or better than metal piping for many uses. One of the drawbacks in using plastic pipe for such services as water and gas mains is the problem of tapping into a plastic pipe while the piping is in service.
Many designs for tapping tee cutters for plastic pipe have been presented, but the majority of these suffer from a disability of requiring application of pressure to preform the cutting operation that is also sufficient to cause deforming of the wall of the plastic pipe that is being cut. The deforming of the wall of the pipe causes the cuts to be sufficiently out of true to permit problems of leakage after the cut is made and the pipe has returned to its true shape against the sadle of the tapping tee.
I have discovered that by minimizing the friction between the external wall of a tapping cutter and the wall of the plastic pipe as the cutter passes through the wall of the pipe that the problem of deforming the wall of the pipe is substantially lessened.
It is therefore an object of this invention to provide a cutter for a tapping tee minimizing frictional contact between the external wall of the cutter and the wall of the plastic pipe through which the cutter is being moved. It is another object of this invention to reduce the probability of deforming plastic pipe during the cutting operation.
Other aspects, objects and the various advantages of this invention will become apparent from a study of the disclosure, the drawing, and the appended claims.